Upper bound on the radii of regular ultra-compact star photonspheres

Abstract

We investigate the photonsphere in the background of regular asymptotically flat compact stars. The analysis includes the general hairy compact star considering the matter fields' backreaction on the metric in various gravity theories. We prove that the photonsphere of the compact star has an upper bound expressed in terms of the ADM mass of the spacetime. In the case of negative isotropic trace, a stronger upper bound can be obtained.

8 pages

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Cited by in corpus (7)

• The extreme orbital period in scalar hairy kerr black holes
• Shadow of quantum extended Kruskal black hole and its super-radiance property
• The existence of null circular geodesics outside extremal spherically symmetric asymptotically flat hairy black holes
• Neutrino trapping in extremely compact Tolman VII spacetimes
• Gravitational lensing inside and outside of a marginally unstable photon sphere in a general, static, spherically symmetric, and asymptotically-flat spacetime in strong deflection limits
• A no-go theorem for scalar fields with couplings from Ginzburg-Landau models
• No scalar condensations outside reflecting stars with coupling terms from Ginzburg-Landau models